The King-in-Parliament (or Queen-in-Parliament when there is a female monarch) is a British constitutional law term for the British Crown in its legislative role, acting with the advice and consent of the House of Commons and House of Lords. The Parliament of the United Kingdom consists of the Crown and the two houses of Parliament, and bills passed by the two houses are sent to the Sovereign for Royal Assent before they become law. These primary acts of legislation are known as Acts of Parliament. An Act may also provide for secondary legislation which can be made by the Crown, subject to the simple approval, or the lack of disapproval, of both houses of Parliament.

The term may also be used in some Commonwealth Realms to refer to the Crown and Parliament of those countries.

A modern British Act of Parliament will typically contain the following enacting clause:

"BE IT ENACTED by the Queen's most Excellent Majesty, by and with the advice and consent of the Lords Spiritual and Temporal, and Commons, in this present Parliament assembled, and by the authority of the same, as follows..."